1. Field of the Invention
This invention relates to a truck with an extendable truck bed and boxes of different lengths. The boxes are readily removable and replaceable successively together with a method of operation thereof.
2. Description of the Prior Art
Trucks with removable and replaceable boxes are known. However, previously known embodiments suffer from one or more disadvantages in that the truck bed cannot accommodate boxes of different lengths; or, the truck bed cannot be extended or retracted to correspond to the length of the box; or, the box is not easily removable and replaceable; or, there is a large gap between the rear of the cab and the front of the box; or, the floor of the box is too high off the ground when the box is loaded on the truck bed in an operating position, thereby causing the truck to have a high centre of gravity; or, the truck is relatively unstable when a box is mounted on the truck bed; or, the box overhangs the truck frame by a substantial amount, thereby greatly reducing the weight on the front wheels on the truck and making the truck difficult to turn; or, the floor of the truck box is not located above a winch; or, the truck with the removable box does not have the same handling capability as a truck with a box that is fixed in position; or, except for connecting or disconnecting the cable, the procedure for unloading a box cannot be controlled from inside the cab of the truck; or, previous trucks are much too expensive or complex.
In one known embodiment, the truck bed has a crane permanently mounted thereon and the crane moves the box onto or off of the truck bed. These trucks are extremely expensive to manufacture. Alternatively, a truck bed can have mounting arms thereon that engage two sides of a truck box for moving the truck box onto the bed or off of the bed. Some previous trucks have boxes that are removed off the side of the truck bed.
It is an object of the present invention to provide a truck having a number of boxes of different lengths that can be successively mounted on the truck and easily removed and replaced.
A truck has an extendable and retractable truck bed to receive truck boxes of different lengths. The truck has a cab and a truck bed located to the rear of the cab. The bed has a raised central portion extending longitudinally. The central portion supports a frame that is connected to a rear of the central portion at a pivot point. At least one hydraulic cylinder extends between the central portion and the frame. The cylinder is capable of tilting the frame rearward relative to the central portion. The truck bed has a winch with an extendable and retractable cable mounted thereon. The truck bed has a truck box removably mounted on the frame. The box having attachment means thereon to receive the cable. The frame has guide means thereon and the box has guide means thereon corresponding to the guide means on the frame. The guide means are oriented so that the box can slide from front to rear and vice versa relative to the frame. The frame has two movable supports that can be extended and retracted longitudinally, the movable supports extending or retracting a length of the truck bed. The movable supports support the truck box when the truck box exceeds a minimum length of the truck bed. The length of the truck bed substantially corresponds to the length of the truck box to be installed on the truck bed. The movable supports also guide the truck box onto or off of the truck bed.
The frame further comprises brackets corresponding to brackets on the truck box that interlock with one another when the truck box is completely mounted on the truck bed.
A method of extending or retracting a length of a truck bed of a truck to receive in succession truck boxes being first truck box and a second truck box, said truck boxes having different lengths, having a cab and a truck bed located to the rear of the cab uses a raised central portion on the truck bed. The central portion supports a frame that is connected to a rear of the central portion at a pivot point. At least one hydraulic cylinder extends between the central portion and the frame. The at least one cylinder is capable of tilting the frame rearward relative to the central portion. The truck bed has a winch with an extendable and retractable cable mounted thereon. Each truck box has attachment means thereon to receive the cable. The frame has guide means thereon and the box has guide means thereon corresponding to guide means on the frame. The frame has two movable supports that can be extended longitudinally to extend a rear of the truck bed or the movable supports can be retracted. The method comprises commencing with said truck boxes located on a supporting surface separate and apart from the truck, backing the truck towards the first truck box so that the truck is generally longitudinally aligned with the first truck box and the front of the first truck box faces the truck bed, tilting the frame upward and rearward relative to the truck bed, operating the winch to extend the cable and attaching the cable to the attachment means on the first truck box, retracting the winch to keep the cable taut, extending the movable supports and backing the truck closer to the first truck box while continuing to retract the cable to keep the cable taut, further extending the movable supports as necessary and continuing to back up the truck until a free end of the movable supports extends slightly within the guide means on the first truck box, retracting the winch further to tighten the cable and pull the first truck box closer to the truck along the movable supports, continuing to retract the cable to pull the truck box forward and upward relative to the truck until the guide means on the first truck box are engaged with the guide means on the frame, continuing to retract the cable to pull the first truck box onto the truck bed while lowering the frame until the front of the truck box is located immediately behind the cab and the frame has been lowered completely relative to the bed, adjusting a length of the movable supports so that a free end thereof extends substantially to a rear of the first truck box, subsequently reversing the method to remove the first truck box from the truck bed, repeating the method to install the second truck box on the truck bed and adjusting the movable supports so that a free end thereof extends substantially to the rear of the second truck box, subsequently reversing the method to remove the second truck box from the truck bed.